This invention relates to a method for manufacturing a spectacle lens for myopes the edge thickness of which is markedly lowered, while some disturbing effects of such spectacle lenses with smaller edge thickness are avoided.
The object of the invention is to provide a method whereby both the aesthetic appearance of the lens is improved and the field of view of such lenses is markedly enlarged relative to other lenses with smaller edge thickness.
Spectacle lenses with a substantial edge thickness, that is a thickness from 7.3 mm to 27 mm are difficult to mount, are thereby very heavy to bear, and simultaneously very unaesthetic because due to the grinding-out of a concave hollow, there appears a very disturbing circle which also results in the well-known bull's-eye effect.
It has already been proposed to lower the lens edge thickness by using with lenses having a high refractive index, a grinding technique which does not however enlarge the field of view. A field of view from 20 to 30 mm at most, depending on the required diopter, is markedly too small. This is however the maximum field of view which is obtained by making use of a technique which is for example the basis for Swiss Patent No. 634,928.
It is further not possible to make use of such a technique for bi- or trifocal lenses, and even less for progressively-varying lenses.
As the concave lens which is machined according to the above-defined method has a too-limited aperture, whereby the locating of the patch for bi- or trifocal lens results in problems which are incompatible with the profile of the concavemachined lens, lenses for myopes treated according to said method may not be designed as bi- or trifocal lenses. This is also the reason why such lens may not be treated as progressive lens either.